The present invention relates to an apparatus for measuring three-dimensional curved surface shapes in a non-contact manner and more particularly to compensation for distortions due to the perspective effect of a television camera.
A three-dimensional curved surface shape measuring method of this type, proposed in U.S. patent application Ser. No. 259,037 the contents of which are incorporated by reference herein, comprises the steps of scanning a linear slit light all over the surface of an object to be measured while rotating the slit light, forming a composite image in which the value of each of picture elements within a picture of a video signal produced by picking up the surface of the object is represented by information relating to the angle of the slit light at the instant that the slit light passes through one of the positions on the object surface corresponding to each picture element and processing the composite image to measure the three-dimensional curved surface shape of the object to be measured.
However, this shape computing method is based on the tacit assumption that the distance between the television camera and the object to be measured is infinitely great or can be considered to be infinitely great. Where the distance between the television camera and the object to be measured is finite and the perspective effect cannot be ignored when observing the object from the television camera as in the actual measuring system, there is a disadvantage that if this shape computing method is applied as such, distortions due to the perspective effect are caused in the shape measurement result obtained.